1. Field of the Invention
The invention relates to methods using hydrogen peroxide and/or ammonia from household chemicals to decontaminate materials which have been contaminated with nerve and mustard chemical warfare agents. The composition is generally non-toxic to handling personnel prior to its use as a decontaminant for chemical warfare agents and can be conveniently made.
2. Background
Over many years, various highly toxic chemical and biological warfare agents have been developed and stockpiled by several nations. These weapons are very efficient in causing multiple casualties and cannot easily be detected, making their production and eventual deployment difficult to monitor. In addition, these weapons cost relatively little to produce and are easy to manufacture. In view of the hazards associated with these agents, it is essential to have formulations which can rapidly and efficiently decontaminate surfaces which have been exposed to these chemical and biological warfare agents. Rapid decontamination minimizes downtime for soldiers operating within a contaminated area.
Several types of toxic chemical compounds are known. These include mustard and nerve agents. Mustard agents or gases, also called blister agents, may be nitrogen or chlorinated sulfur compounds. The most common type of mustard agents are the chlorinated sulfur compounds. Long after mustard gas was discovered in 1822, it was used in World War I as a chemical warfare agent, causing approximately 400,000 casualties. The sulfur mustard gas is chemically known as bis-(chloroethyl)-sulfide. The nitrogen mustard gas is chemically known as tris(2-chloroethyl)amine. Mustard gas is a colorless, oily liquid having a garlic or horseradish odor. It is slightly soluble in water, complicating removal by washing. It primarily attacks humans through inhalation and dermal contact, having an Airborne Exposure Limit (AEL) of 0.003 mg/m3. Mustard gas is a vesicant and an alkylating agent which produces a cytotoxic reaction to the hematopoietic tissues. Symptoms usually begin to take effect 4 to 24 hours after initial contact. The rate of detoxification of mustard gas is slow and repeated exposure yields a cumulative effect.
Nerve agents or gases were discovered in 1936, during research on more effective pesticides. Nerve agents inhibit a certain enzyme within the human body from destroying a substance called acetylcholine. This produces a nerve signal within the body forcing the muscles to contract. Nerve agents have an Airborne Exposure Limit (AEL) of 0.00001 mg/m3.
An important aspect of any containment strategy is to be able to neutralize the threat using chemical decontamination methods. Most chemical warfare agents (CWA's) and biological warfare agents (BWA's) can be destroyed or rendered harmless by suitable chemical treatments. Unfortunately, existing chemical treatments for neutralization of biological and chemical agents have significant drawbacks. “Universal” formulations are desired that can decontaminate all biological and chemical threats in all environments and on all surfaces. Existing decontamination solutions may only be effective against a certain class of agents. Although basic peroxide has been shown to decontaminate GD and GB, it does not individually affect HD, because of both its insolubility in aqueous media and its slow reaction with OOH−. It has been reported in “Catalytic Activation of Hydrogen Peroxide-A Green Oxidant System,” by Russell S. Drago, Karen M. Frank, George Wagner, and Yu-Chu Yang in Proceedings of the 1997 ERDEC Scientific Conference on chemical and Biological Defense Research, ERDEC-SP-063, Aberdeen Proving Grounds, Md., July 1998, pp. 341-342, that bicarbonate ion dramatically enhances the oxidation of HD by peroxide in water/t-BuOH media via generation of the highly reactive peroxocarbonate, HCO4−.
To be effective, emergency response personnel may need several types of decontaminants available on-hand. Use of existing decontaminants under inappropriate conditions can result in the formation of dangerous by-products. For example, a dilute bleach solution is very effective at destroying anthrax spores, but an extremely toxic by-product is formed if used to destroy VX. Furthermore, some chemicals, such as sodium hydroxide dissolved in organic solvents are unsuitable for use in certain conditions because they corrode, etch or erode materials.
Today, many different types of CWA's and BWA's are known. The CWA's fall into three main classes: sulfur mustards (HD), nitrogen mustards (HN3), and organophosphorous nerve agents (acetylcholinesterase inhibitors) of the G (GA, GB, GD, GE, GF) and V (VX, VE, VG, VM) type. BWA's can be classified into at least five categories: viruses, bacteria, rickettsia, biological toxins, and genetically engineered agents.
Most decontamination processes include some form of hydrolysis. Hydrolysis of CWA's creates intermediates or by-products of organophosphorous compounds that are sometimes more toxic than the agent itself. While hydrolysis may be acceptable for many organophosphorous compounds, it is not universally effective against all of these compounds and great care must be taken to first identify then treat the agent under the proper hydrolyzing conditions.
The oxidation of neutral organo-phosphorous esters (OPEs) usually involves atoms other than phosphorus. In compounds containing sulfur, oxidation generally occurs at the sulfur atom. In unprotected nitrogen moieties, oxidation at nitrogen will occur and may result in increased inhibition of acetylcholine esterase. From a toxicological standpoint, random oxidation of organophosphorous compounds at critical sites could result in the production of better esterase inhibitors.
These considerations highlight the need for a system capable of decontaminating a broad range of chemical and biological agents without producing toxic by-products. In addition, there is a need for a decontamination system that is compatible with most common materials, easy to dispense and environmentally safe.
Chemical Warfare Agents are exceedingly toxic and must be decontaminated following either attacks—military or terrorist—or accidental spills. Porous surfaces such as concrete are most difficult to decontaminate as the chemical agents become sorbed into the material where they remain contact and vapor hazards for extended periods of time.
Hydrogen peroxide is an ideal reactive material for decontamination—especially in the environment—since it decomposes to yield harmless, environmentally friendly oxygen and water. Moreover, no residue is left behind following its use.
It is well-known that G agents are easily and quickly decontaminated by both dilute base and basic hydrogen peroxide, as disclosed in Wagner et al., Decontamination of VX, GD, and HD on a Surface Using Modified Vaporized Hydrogen Peroxide, Langmuir 2007, 23, 1178-1186, incorporated herein by reference in its entirety. Ammonia (NH3), a gas, is known to form basic solutions when dissolved in water. Further, it is widely used as a fertilizer in agriculture and as the active ingredient in household cleaning products (see below) and is the active ingredient in smelling salts. In fact, ammonia's potent, distinct aroma has been experienced by practically everyone and is quite recognizable.
Current peroxide-based decontaminants are DF200 and DECON GREEN. DECON GREEN is a reactive, universal decontaminant for VX, HD, and G agents composed of bicarbonate (baking soda), hydrogen peroxide, alcohol, and/or other ingredients as disclosed by Wagner et al, Feasibility of Formulating DECON GREEN with Aircraft Deicing Fluid: VX, GD, and HD Reactivity, Geo-Centers Inc. Aberdeen Proving Ground Md., Report No. A897234, Contract No. DAAM01-98-C-0008, Report Date January 2005, incorporated herein by reference in its entirety. A method of use of DECON GREEN decontaminant is also covered by U.S. Pat. No. 6,245,957 incorporated herein by reference in its entirety. U.S. Pat. No. 6,245,957 claims a method of neutralizing chemical warfare agents, comprising the steps of: providing a composition comprising a mixture of potassium bicarbonate, a solid urea hydrogen peroxide component, and an alcohol component wherein said alcohol is selected from the group consisting of ethanol, isopropanol, propylene glycol, polypropylene glycol and derivates thereof; and, contacting a chemical warfare agent with said composition.
However, current peroxide-based decontaminants such as DF200 and DECON GREEN require industrial-strength concentrations of aqueous hydrogen peroxides, i.e. 8 to 35%. Thus, these decontaminants are hazardous to store, ship and handle, requiring caution on the part of the end-user. In addition to the hydrogen peroxide component, such decontaminants utilize many other ingredients with which the typical end-user has no prior experience or knowledge. Being able to formulate efficacious decontaminants with benign items used by people in everyday life, and which are readily available at any supermarket, would have obvious advantages.
The common chemical warfare agents for which decontaminants are routinely used to demonstrate efficacy are the nerve agents VX and GD, and the blister agent HD. GD, being water-soluble and easily decontaminated by dilute base, is perhaps the easiest to destroy. Although VX is also water-soluble like GD, it cannot be decontaminated by dilute base as the toxic EA-2192 byproduct is formed. EA-2192 is S-(2-diisopropylaminoethyl)methylphosphonothioic acid.
Basic peroxide, which contains the particularly reactive peroxyanion (OOH−) species, is much more effective against VX as formation of EA-2192 is eliminated by use of this reactant. HD is water-insoluble, but can be slowly hydrolyzed in water with sufficient and prolonged agitation. Yet a much faster method for decontaminating HD is via single-oxidation to its non-vesicant sulfoxide, which can be very fast compared to hydrolysis. However, care must be taken to perform the oxidation selectively, so as to not further oxidize the sulfoxide to the vesicant sulfone. Fortunately, dilute hydrogen peroxide possesses the needed selectivity to initially selectively oxidize HD to the sulfoxide, avoiding formation of the sulfone.